1. Field of the Invention
The present invention relates to a power conversion apparatus and a dead time generator. For example, the present invention can be applied to an apparatus using paired switching elements such as an AC-DC converter or DC-DC converter.
2. Description of the Related Art
As a power supply circuit (power conversion apparatus) for obtaining a DC output from the commercial power supply (AC input), there is one described in Japanese Patent Laid-Open No. 4-364362.
The power supply circuit described in Japanese Patent Laid-Open No. 4-364362 includes a DC power supply obtained from the commercial power supply (AC input) by conversion; switching means including a switching element, which can be controlled to turn on and off, to switch the DC power supply, convert the DC power supply to AC and output the AC; DC output means for conducting full-wave rectification on a supplied AC input, then conducting smoothing using a capacitor, and taking out a DC output; series resonance means formed in series between an output terminal of the switching means and an input terminal of the DC output means; parallel resonance means formed in parallel across the switching element in the switching means; and timing control means, which exercises control to periodically turn on and off the switching element in the switching means, after turning on the switching means, which exercises control to turns off the switching means after a current flowing through the switching means has become approximately zero due to end of series resonance in the series resonance means, after turning off the switching means, which exercises control to turns on the switching means after a voltage applied to the switching means has changed and become approximately zero due to parallel resonance in the parallel resonance means.
However, the above-described conventional circuit adopts self-excited zero-cross switching in which the switching means is switched after the voltage resonance and the current resonance have become approximately zero. Therefore, there is a problem that its general configuration becomes complicated and setting of characteristic values in respective elements is severe.
Furthermore, the zero-cross switching operation adopted by the conventional circuit has a problem in that it causes an increased peak current, a poor power factor, and a poor power conversion efficiency.
In addition, if a plurality of power supply circuits are operated in parallel and the conventional circuit is applied to each of the power supply circuits, there is a problem that the power supply circuits conduct switching operation independently and individually, and it is difficult to operate the power supply circuits in synchronism.
In addition, in the conventional circuit, the parallel resonance means is provided in parallel across the switching element in the switching means. Therefore, it is difficult to raise the frequency and size reduction of the whole configuration is obstructed.